Re: [PATCH] mtd: spi-nor: Don't copy self-pointing struct around

[Tudor.Ambarus]

On 10/5/20 11:48 AM, Alexander A Sverdlin wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> From: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>
> 
> spi_nor_parse_sfdp() modifies the passed structure so that it points to
> itself (params.erase_map.regions to params.erase_map.uniform_region). This
> makes it impossible to copy the local struct anywhere else.
> 
> Therefore only use memcpy() in backup-restore scenario. The bug may show up
> like below:
> 
> BUG: unable to handle page fault for address: ffffc90000b377f8
> Oops: 0000 [#1] PREEMPT SMP NOPTI
> CPU: 4 PID: 3500 Comm: flashcp Tainted: G           O      5.4.53-... #1
> ...
> RIP: 0010:spi_nor_erase+0x8e/0x5c0
> Code: 64 24 18 89 db 4d 8b b5 d0 04 00 00 4c 89 64 24 18 4c 89 64 24 20 eb 12 a8 10 0f 85 59 02 00 00 49 83 c6 10 0f 84 4f 02 00 00 <49> 8b 06 48 89 c2 48 83 e2 c0 48 89 d1 49 03 4e 08 48 39 cb 73 d8
> RSP: 0018:ffffc9000217fc48 EFLAGS: 00010206
> RAX: 0000000000740000 RBX: 0000000000000000 RCX: 0000000000740000
> RDX: ffff8884550c9980 RSI: ffff88844f9c0bc0 RDI: ffff88844ede7bb8
> RBP: 0000000000740000 R08: ffffffff815bfbe0 R09: ffff88844f9c0bc0
> R10: 0000000000000000 R11: 0000000000000000 R12: ffffc9000217fc60
> R13: ffff88844ede7818 R14: ffffc90000b377f8 R15: 0000000000000000
> FS:  00007f4699780500(0000) GS:ffff88846ff00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffffc90000b377f8 CR3: 00000004538ee000 CR4: 0000000000340fe0
> Call Trace:
>  part_erase+0x27/0x50
>  mtdchar_ioctl+0x831/0xba0
>  ? filemap_map_pages+0x186/0x3d0
>  ? do_filp_open+0xad/0x110
>  ? _copy_to_user+0x22/0x30
>  ? cp_new_stat+0x150/0x180
>  mtdchar_unlocked_ioctl+0x2a/0x40
>  do_vfs_ioctl+0xa0/0x630
>  ? __do_sys_newfstat+0x3c/0x60
>  ksys_ioctl+0x70/0x80
>  __x64_sys_ioctl+0x16/0x20
>  do_syscall_64+0x6a/0x200
>  ? prepare_exit_to_usermode+0x50/0xd0
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> RIP: 0033:0x7f46996b6817
> 
> Fixes: 1c1d8d98e1c7 ("mtd: spi-nor: Split spi_nor_init_params()")

I think the correct Fixes tag is:
Fixes: c46872170a54 ("mtd: spi-nor: Move erase_map to 'struct spi_nor_flash_parameter'")

> Cc: stable@xxxxxxxxxxxxxxx
> Tested-by: Baurzhan Ismagulov <ibr@xxxxxxxxxxx>
> Co-developed-by: Matija Glavinic Pecotic <matija.glavinic-pecotic.ext@xxxxxxxxx>
> Signed-off-by: Matija Glavinic Pecotic <matija.glavinic-pecotic.ext@xxxxxxxxx>
> Signed-off-by: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>
> ---
>  drivers/mtd/spi-nor/core.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> index 2add4a0..cce0670 100644
> --- a/drivers/mtd/spi-nor/core.c
> +++ b/drivers/mtd/spi-nor/core.c
> @@ -2701,11 +2701,10 @@ static void spi_nor_sfdp_init_params(struct spi_nor *nor)
> 
>         memcpy(&sfdp_params, nor->params, sizeof(sfdp_params));
> 
> -       if (spi_nor_parse_sfdp(nor, &sfdp_params)) {
> +       if (spi_nor_parse_sfdp(nor, nor->params)) {
> +               memcpy(nor->params, &sfdp_params, sizeof(*nor->params));
>                 nor->addr_width = 0;
>                 nor->flags &= ~SNOR_F_4B_OPCODES;
> -       } else {
> -               memcpy(nor->params, &sfdp_params, sizeof(*nor->params));

neat!
With the Fixes tag fixed, one can add:
Reviewed-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxxxxx>

>         }
>  }
> 
> --
> 2.10.2
>